The objectives of the project are elucidation of the genetic fine structural organization of the eukaryotic chromosome and of the eukaryotic gene. Hypotrichous ciliated protozoa are used because the chromosomes in a micronucleus are cut up into gene-sized pieces of DNA to make a macronucleus. In the process about 95% of the nucleotide sequences of micronucleus are destroyed (as determined by renaturation kinetics) yet the macronucleus contains all of the genetic information for growth, division, and maintenance of the cell. We propose that chromosomes consist of genes separated by long DNA spacers of unknown function (but are not control regions for genes or genetic in the usual sense). The putative spacers are similar to the transcribed and non-transcribed spacers, of unknown function, that are present in and between transcription units for ribosomal RNAs and tRNAs. The gene-sized pieces of DNA in the macronucleus have an average molecular weight of 3 times 10 to the sixth power daltons, have one RNA polymerase binding site, and contain two single-strand nicks, one in each chain. Palindromic sequences and half-palindromes are present at the nicks and ends repectively, such that renaturation of single-stranded DNA leads to formation of single-stranded circular molecules. We are sequencing the palindromic sequences, searching for the restriction enzyme(s) that convert chromosomal DNA to gene-sized DNA, and analyzing our model of chromosome organization by in situ hybridization at the electron microscope level. BIBLIOGRAPHIC REFERENCES; DNA of Ciliated Protozoa; DNA Sequence Diminution during Macronuclear Development of Oxytricha. 1976. Cell 7, 67-74. M.R. Lauth, B.B. Spear, J. Heumann, and D.M. Prescott, Conjugation in the Hypotrich Ciliate, Paraurostyla weissei (Stein); A Scanning Electron Microscope Study. 1975. The J. of Protozool. 22(3), 392-397. John Heumann.